package com.app.encryption;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.spec.SecretKeySpec;

/**
 * Author: ZhuWenWu Version V1.0 Date: 14-3-16 下午4:43 Description: AES加密类 Modification History: Date Author Version
 * Discription ----------------------------------------------------------------------------------- 14-3-16 ZhuWenWu 1.0
 * 1.0 Why & What is modified:
 */
public class AesEncryption {
	
	private final static String HEX = "0123456789ABCDEF";

	//加密字符串
	public static String encrypt(String seed, String clearText) throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] result = encrypt(rawKey, clearText.getBytes());
		return toHex(result);
	}

	//加密字节流
	public static byte[] encryptByte(byte[] seed, byte[] clearText) throws Exception {
		byte[] rawKey = getRawKey(seed);
		return encrypt(rawKey, clearText);
	}

	//解密字符串
	public static String decrypt(String seed, String encrypted) throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] enc = toByte(encrypted);
		byte[] result = decrypt(rawKey, enc);
		return new String(result);
	}

	//解密字节流
	public static byte[] decryptByte(byte[] seed, byte[] encrypted) throws Exception {
		byte[] rawKey = getRawKey(seed);
		return decrypt(rawKey, encrypted);
	}

	private static byte[] getRawKey(byte[] seed) throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
		sr.setSeed(seed);
		kgen.init(128, sr); // 192 and 256 bits may not be available
		return kgen.generateKey().getEncoded();
	}

	public static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
		return cipher.doFinal(clear);
	}

	public static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.DECRYPT_MODE, skeySpec);
		return cipher.doFinal(encrypted);
	}

	public static String toHex(String txt) {
		return toHex(txt.getBytes());
	}

	public static String fromHex(String hex) {
		return new String(toByte(hex));
	}

	public static byte[] toByte(String hexString) {
		int len = hexString.length() / 2;
		byte[] result = new byte[len];
		for (int i = 0; i < len; i++)
			result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2), 16).byteValue();
		return result;
	}

	public static String toHex(byte[] buf) {
		if (buf == null) return "";
		StringBuffer result = new StringBuffer(2 * buf.length);
		int size = buf.length;
		for (int i = 0; i < size; i++) {
			appendHex(result, buf[i]);
		}
		return result.toString();
	}

	private static void appendHex(StringBuffer sb, byte b) {
		sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
	}
}
